Current aircraft practice in high lift devices has standardized on wing leading edge slats and slots, and wing trailing edge flaps of the fixed hinge or Fowler flap variety. The most advanced of these high lift systems combine both leading and trailing edge devices which can change both the camber and chord of the associated wing. The least advanced devices are found on private aircraft and are usually confined to single unit trailing edge flaps with fixed hinge points.
Most advanced and least advanced trailing edge flaps operate in airflow below the wing. However, airflow above the wing is critical in the prevention of stalls and there has been much experimentation in the boundary layer bleed approach, but little practical application.
Examples of various forms of wing flap constructions are disclosed in U.S. Pat. Nos. 2,289,704, 2,549,760, 2,852,211, 3,184,186, 3,260,477, 3,586,267, 3,706,431 and 3,827,657.